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pi

(PHP 4, PHP 5)

piGet value of pi

Description

float pi ( void )

Returns an approximation of pi. The returned float has a precision based on the precision directive in php.ini, which defaults to 14. Also, you can use the M_PI constant which yields identical results to pi().

Return Values

The value of pi as float.

Examples

Example #1 pi() example

<?php
echo pi(); // 3.1415926535898
echo M_PI// 3.1415926535898
?>


User Contributed Notes
pi
ghostt dot ew at gmail dot com
10-Feb-2010 12:05
The highest current precision you can get from pi() at this point is 49 digits.

<?php

$precision
= 49;
ini_set("precision", $precision);
echo
pi(); //will output 3.141592653589793115997963468544185161590576171875

?>
gmail user robkohr
05-Dec-2008 11:38
<?php
/*
 Returns angle of line segment in degrees. Angle will be a positive
 value between 0 and 360. 0 will be north, 90 east, 180 south, 270 west
 Author: Robert Kohr
*/
function get_angle($x1, $y1, $x2, $y2, $negative_y_is_up=0){
 
//differences in x and y
 
$x = $x2 - $x1;
 
$y = $y2 - $y1;
 
//y will need to be negated for where + y is down
 
if($negative_y_is_up){
   
//useful in some applications
   
$y = -$y;
  }
  return (
rad2deg(atan2($x, $y))+360)%360;
}
?>
Keamos at gmail
14-Jan-2006 05:31
For anyone wondering, the highest precision you can get for pi() or M_PI is 20 places after the decimal point, or 3.14159265358979323846.
davidduke at hotmail dot com
28-Mar-2004 02:18
Pi is often usefull in con/sin/tan functions..
There are also other Pi related constants.
These are most of them:

M_PI  = 3.14159265358979323846 // pi

// The following were added in PHP 4.0.0
M_PI_2 = 1.57079632679489661923 // pi/2
M_PI_4 = 0.78539816339744830962 // pi/4
M_1_PI = 0.31830988618379067154 // 1/pi
M_2_PI = 0.63661977236758134308 // 2/pi
M_SQRTPI = 1.77245385090551602729 // sqrt(pi) (Only in PHP 4.0.2+)
M_2_SQRTPI = 1.12837916709551257390 // 2/sqrt(pi)
 

 
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